.\" -*- nroff -*-
.\" Copyright 2010 Cisco Systems, Inc.  All rights reserved.
.\" Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines
.\" Copyright (c) 2020      Google, LLC. All rights reserved.
.\" $COPYRIGHT$
.TH MPI_Comm_get_name 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
.SH NAME
\fBMPI_Comm_get_name\fP \- Returns the name that was most recently associated with a communicator.

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
int MPI_Comm_get_name(MPI_Comm \fIcomm\fP, char *\fIcomm_name\fP, int *\fIresultlen\fP)

.fi
.SH Fortran Syntax
.nf
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMM_GET_NAME(\fICOMM, COMM_NAME, RESULTLEN, IERROR\fP)
	INTEGER	\fICOMM, RESULTLEN, IERROR \fP
	CHARACTER*(*) \fICOMM_NAME\fP

.fi
.SH Fortran 2008 Syntax
.nf
USE mpi_f08
MPI_Comm_get_name(\fIcomm\fP, \fIcomm_name\fP, \fIresultlen\fP, \fIierror\fP)
	TYPE(MPI_Comm), INTENT(IN) :: \fIcomm\fP
	CHARACTER(LEN=MPI_MAX_OBJECT_NAME), INTENT(OUT) :: \fIcomm_name\fP
	INTEGER, INTENT(OUT) :: \fIresultlen\fP
	INTEGER, OPTIONAL, INTENT(OUT) :: \fIierror\fP

.fi
.SH INPUT PARAMETER
.ft R
.TP 1i
comm
Communicator the name of which is to be returned (handle).
.TP 1i

.SH OUTPUT PARAMETER
.ft R
.TP 1i
comm_name
Name previously stored on the communicator, or an empty string if no such name exists (string).
.TP 1i
resultlen
Length of returned name (integer).
.TP 1i
IERROR
Fortran only: Error status (integer).

.SH DESCRIPTION
.ft R
MPI_Comm_get_name returns the last name that was previously associated with the given communicator. The name may be set and retrieved from any language. The same name will be returned independent of the language used. \fIcomm_name\fP should be allocated so that it can hold a resulting string of length MPI_MAX_OBJECT_NAME characters. MPI_Comm_get_name returns a copy of the set name in \fIcomm_name\fP.
.sp
If the user has not associated a name with a communicator, or an error occurs, MPI_Comm_get_name will return an empty string (all spaces in Fortran, "" in C). The three predefined communicators will have predefined names associated with them. Thus, the names of MPI_COMM_WORLD, MPI_COMM_SELF, and MPI_COMM_PARENT will have the default of MPI_COMM_WORLD, MPI_COMM_SELF, and MPI_COMM_PARENT. The fact that the system may have chosen to give a default name to a communicator does not prevent the user from setting a name on the same communicator; doing this removes the old name and assigns the new one.

.SH NOTES
.ft R
It is safe simply to print the string returned by MPI_Comm_get_name, as it is always a valid string even if there was no name.
.sp
Note that associating a name with a communicator has no effect on the semantics of an MPI program, and will (necessarily) increase the store requirement of the program, since the names must be saved. Therefore, there is no requirement that users use these functions to associate names with communicators. However debugging and profiling MPI applications may be made easier if names are associated with communicators, since the debugger or profiler should then be able to present information in a less cryptic manner.

.SH ERRORS
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.
.sp
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.

